Microwave coagulation applicator and system

ABSTRACT

A microwave applicator for insertion into living body tissue for use in microwave coagulation and ablation treatments includes a microwave transmission line extending between an attachment end of the applicator and an antenna toward an insertion end of the applicator with an outer conductive sleeve forming an enclosed cooling fluid space around the transmission line. Circulation of cooling fluid is guided in the cooling fluid space by a guide sleeve. A temperature sensor senses the approximate temperature of cooling fluid to indicate cooling fluid is circulating. A multiplexing and power splitting circuit provides outputs tuned for one or for more than one applicator to be attached and detects the number of applicators and correct connection. A cadence sound generator can be used in conjunction with depth markings on the applicator to provide substantially constant withdrawal of the applicator from the treated tissue after treatment to provide track ablation.

BACKGROUND OF THE INVENTION

1. Field

This invention relates to electromagnetic radiation (EMR) therapy andmore particularly to applicators and systems for applyingelectromagnetic energy to a treatment site in a living body to heattissue needing treatment at the treatment site. The invention is usefulparticularly for treatments in the nature of microwave coagulation orablation.

2. State of the Art

The use of electromagnetic (EM) energy to heat tissue for the treatmentof disease is known. In using microwave energy for tissue heating, anapplicator having a microwave radiating antenna is positioned withrespect to the tissue to be treated (heated) so that microwave energyradiated from the antenna penetrates and heats the tissue. Manymicrowave applicators are known in the art. Death, or necrosis, ofliving tissue cells occurs at temperatures elevated above a normal celltemperature for a sufficient period of time. The sufficient period oftime is generally dependent upon the temperature to which the cells areheated. Above a threshold temperature of about 41.5 degrees C.,substantial thermal damage occurs in most malignant cells. Attemperatures above about 45 degrees C. thermal damage occurs to mostnormal cells. During treatment, it is desirable to produce an elevatedtemperature within the targeted tissue for a time period sufficient tocause the desired cell damage, while keeping nearby healthy tissue at asafe lower temperature. For this reason, when treatment involving tissueheating is used, it is important to assure both adequate tumor heatingthroughout the tumor to the tumor margin and reduced temperatures in thecritical normal tissue.

Heating therapy is sometimes combined with other treatments, such assurgery, ionizing radiation, and chemotherapy. For example, when heatingis combined with radiation, it is desirable to maintain the temperaturewithin the diseased tissue within the range of about 42 to 45 degrees C.Higher temperatures are usually undesirable when a combined treatmentmodality is used because higher temperatures can lead to microvessalcollapse causing resistance to radiation therapy and decrease the amountof systemic chemotherapy from reaching the tumor if it has vasculardamage. Lower temperatures are undesirable because they can fail toprovide adequate therapeutic effect. Therefore, it is important tocontrol the temperature within the desired range for multi-modalitytreatments and not allow heating of the tissue in the tumor or aroundthe tumor to above 45 degrees C. if such tissue damage from othertreatments may be compromised. Treatment within this controlledtemperature range is usually referred to as hyperthermia.

Forms of thermal therapy that kill the tissue with heating alone aregenerally referred to as coagulation or ablation. To adequatelyeradicate a cancerous tumor with only the application of heat, it isnecessary to ensure adequate heating is accomplished throughout theentire tumor. In cases of a malignant tumor, if viable tumor cells areleft behind, the tumor can rapidly grow back leaving the patient withthe original problem. In what is generally referred to as microwavecoagulation or microwave ablation, the diseased tissue is heated to atleast about 55 degrees C., and typically above about 60 degrees C., forexposure times sufficient to kill the cells, typically for greater thanabout one minute. With microwave coagulation and ablation treatments,there is a volume reduction of temperature that ranges from the hightemperature in the treated tissue to the normal tissue temperature of 37degrees C. outside the treated tissue. The outer margin of the overallheat distribution in the treated tissue volume may then result in damageto normal tissue if such normal tissue is overheated. Therefore, forprolonged coagulation or ablation treatments where the coagulation orablation volume is maintained at very high temperatures, there is a highrisk of damage to surrounding normal tissues. For proper treatment oftargeted cancerous tumor volumes or other tissue volumes to be treated,it becomes very important to properly deliver the correct thermaldistribution over a sufficient time period to eradicate the tumor tissuewhile minimizing damage to critical surrounding normal tissue.Fortunately, there are tumor locations that reside in normal tissue thatcan be destroyed by the heating in limited areas without affecting thehealth of the patient, such as liver tissue. In such situations thecoagulation can be applied in an aggressive way to include a margin ofsafety in destruction of limited surrounding normal tissues to assurethat all of the cancerous tumor is destroyed.

The process of heating very rapidly to high temperatures that is commonin coagulation and ablation treatments may utilize a rather shortexposure time. In doing so, the resulting temperature distributionbecomes primarily a result of the power absorption distribution withinthe tissue. However, if such treatments continue for multiple minutes,the blood flow and thermal conduction of the tumor and surroundingtissues will modify the temperature distribution to result in a lesspredictable heat distribution because the changes occurring in bloodflowin such a heated region may not be predictable. Therefore, it isimportant to optimize the uniformity of the tissue heating power that isabsorbed to lead to a more predictable temperature distribution thatbetter corresponds with the treatment prescription. Therefore,pretreatment planning practices prior to and possibly during treatmentfor calculating the power and temperature distribution resulting fromthe parameters of power and relative phase of the power applied to thetissue can be important for not only coagulation and ablation, but alsohyperthermia. As higher temperatures are used during treatment, it mayincrease patient discomfort and pain, so it can be helpful to avoidexcessive temperatures to reduce the need of patient sedation.

Invasive microwave energy applicators can be inserted into living bodytissue to place the source of heating into or adjacent to a diseasedtissue area. Invasive applicators help to overcome some difficultiesthat surface applicators experience when the target tissue region islocated below the skin (e.g., the prostrate). Invasive applicators mustbe properly placed to localize the heating to the vicinity of thedesired treatment area. Even when properly placed, however, it has beendifficult to ensure that adequate heat is developed in the diseasedtissue without overheating surrounding healthy tissue. Further, withapplicators operating at higher power levels to produce the neededhigher temperatures for coagulation and ablation, there is a tendencyfor the coaxial cable in the portion of the applicator leading fromoutside the body to the location of the radiating antenna in theapplicator to heat to undesirably high temperatures which can causethermal damage to the normal tissue through which the applicator passesto reach the diseased tissue to be treated. Therefore, various ways ofcooling the applicator have been used in the prior art.

While many microwave applicators are known in the art for applyingmicrowave energy to tissue to provide heating to the tissue, there is aneed for better applicators that are easy to use, that have moreconsistent and predictable heating patterns, have effective cooling ofthe applicator shafts, and can provide track coagulation or ablation, ifdesired.

SUMMARY OF THE INVENTION

According to the invention, a microwave applicator for use in microwavecoagulation and ablation treatments includes an elongate applicator bodyhaving an insertion end for insertion into a tissue region of a livingbody and an attachment end for attachment to a source of microwaveenergy. An antenna for radiating microwave energy into tissue to betreated is disposed toward the insertion end of the elongate applicatorbody. A coaxial microwave energy transmission line is disposed withinthe applicator body to conduct microwave energy from the attachment endof the applicator to the antenna. An outer conductive sleeve forms theoutside of a portion of the applicator body and is spaced concentricallyaround the microwave energy transmission line to form a cooling fluidspace between the inside surface of the outer conductive sleeve and theouter surface of the microwave energy transmission line. A guide sleeveis positioned concentrically within this cooling fluid space and spacedinwardly from the outer conductive sleeve and around the outside of andspaced outwardly from the microwave energy transmission line. The guidesleeve guides flow of a circulating cooling fluid along the outsidesurface of the microwave energy transmission line and the inside surfaceof the outer conductive sleeve to cool the microwave energy transmissionline and the conductive outer sleeve to maintain the portion of theapplicator extending between the outside of the living body and thetissue to be treated in the living body at a temperature below thatwhich will damage healthy tissue. A temperature sensor is positioned tomeasure the approximate temperature of the circulating cooling fluidthereby indicating that the microwave energy transmission line and theouter conductive sleeve are being actively cooled during the microwavecoagulation or ablation treatment. By monitoring the approximatetemperature of the cooling fluid, the heating of the tissue along theinsertion track of the applicator where inserted into the living body tothe diseased tissue can be better controlled to ensure that damage tosurrounding normal tissue is minimized during treatments. Becausecooling is not normally needed in the tissue to be heated duringcoagulation and ablation treatments, cooling is not provided in the areaof the radiating antenna of the applicator where the heating of tissueis desired.

In one embodiment of the present invention, a microwave applicator forheat treatment of diseased tissue within a living body includes a handleby which the applicator can be held and manipulated for insertion intothe living body. An elongate applicator body having an insertion end forinsertion into a tissue region of the living body extends from thehandle which usually forms the attachment end of the applicator. Anantenna is disposed toward the insertion end of the applicator body.Microwave energy is conducted from the handle to the antenna via amicrowave energy transmission line in the form of a coaxial cabledisposed within the applicator body. The coaxial cable includes an innerconductor and an outer conductor separated by a dielectric materialtherebetween. An outer conductive sleeve extends from the handle to aninsertion end of the outer conductive sleeve which is separated from theconductive tip by a gap, usually filled with a dielectric material. Theoutside diameters of the insertion tip, the outer conductive sleeve, andthe dielectric material filling the gap therebetween are all about equalso as to form a substantially smooth continuous elongate applicatorbody, for insertion into the living body. The elongate applicator body,or at least the portion thereof to be inserted into a living body, maybe coated with a stick resistant dielectric material such as Teflon.This can at least partially reduce the sticking of coagulation tissue tothe applicator outer surface, particularly in the areas of tissuecoagulation and ablation, to facilitate removal of the applicator aftertreatment.

In the illustrated example embodiment, the elongate applicator bodyextending from the handle will be substantially rigid. The outerconductive sleeve may be made of a metal such as stainless steel. Theconductive insertion tip of the applicator will also be metal, such asbrass or stainless steel, and may be sharpened sufficiently so that theapplicator can be inserted directly into tissue to be treated. However,even when sharpened, the applicator will generally not be inserteddirectly through the tough tissue of the skin, but will usually requirethat a cut or an opening, such as made by a hypodermic needle insertedthrough the skin, first be made and then the applicator is insertedthrough such cut or opening. Further, in the illustrated exampleembodiment, a conductive metal shunt is positioned at the insertion endof the conductive outer sleeve to extend toward the insertion tip. Theshunt is also electrically coupled to the outer conductor of themicrowave energy transmission line, thereby electrically coupling theouter conductor of the microwave energy transmission line to theconductive outer sleeve. The insertion tip is secured to, but separatedfrom, the insertion end of the shunt by a substantially rigid dielectricspacer that has structural stiffness to prevent bending of the jointbetween the shunt and tip and to electrically insulate the tip, which iselectrically coupled to the microwave energy transmission line innerconductor, from the shunt, which is electrically coupled to themicrowave energy transmission line outer conductor. The substantiallyrigid dielectric spacer is bonded to the shunt and applicator tip, suchas by an epoxy adhesive.

A non-conductive guide sleeve extends from the handle and is positionedconcentrically within the elongate applicator body inside and spacedinwardly from the outer conductive sleeve and around the outside of andspaced outwardly from the microwave energy transmission line, i.e.,outwardly from the outer conductor thereof. The guide sleeve guides flowof a circulating cooling fluid from the handle along the outside surfaceof the coaxial microwave transmission line to the end of the guidesleeve toward the insertion end of the applicator, around the end of theguide sleeve, and back along the inside surface of the outer conductivesleeve to the handle. An opposite flow of the cooling fluid can also beused. Circulation of cooling fluid cools the coaxial microwavetransmission line and the conductive sleeve to maintain the portion ofthe applicator extending between the outside of the living body and thetissue to be treated in the living body at a temperature below thatwhich will damage healthy tissue. A temperature sensor is positioned,such as in the handle, to measure the approximate temperature of thecooling fluid being circulated in the applicator. The temperature of thecooling fluid in the applicator is an indication of whether or not thefluid circulation system is operating and whether it is coolingsufficiently.

Supply and return connections for the cooling fluid from a pressurizedsource of cooling fluid, usually through flexible hoses, are provided inthe handle. Also, a connection to connect to a source of microwavepower, such as through a flexible coaxial cable, is also provided in thehandle. The handle serves as an interface between the more flexiblecoaxial cable extending from a microwave generator and the more flexiblefluid hoses from a source of cooling fluid, and the substantial rigidelongate applicator.

The temperature sensor used in the applicator may be a thermistor. Theresistance of a thermistor varies with the temperature of thethermistor. The temperature measured by the thermistor is obtained by anexternal circuit that measures the temperature by causing a constant dccurrent to flow through the thermistor. The resistance of the thermistorthen produces a dc voltage that is indicative of the temperature of thethermistor. The temperature sensor in the handle, or a temperaturesensor positioned along the applicator, may be coupled to the flexiblecoaxial cable extending from the microwave generator through a couplingnetwork, such as a resistive and capacitive coupling network. Theresistive and capacitive coupling network allows a dc current from thecoaxial cable conductors to flow to and from the thermistor whileisolating the thermistor from the microwave power signals, and allowsthe microwave power signals to flow to the antenna while isolating theantenna from the dc current. Similarly, a coupling network can be usedat the opposite end of the flexible coaxial cable, such as in powersplitting and multiplexing circuitry, to separate the dc temperaturesignals from the flexible coaxial cable conductors and direct them totemperature sensing circuitry in a system controller while isolating thetemperature sensing circuitry from the microwave power signals, andpassing the microwave power signals from the system microwave generatorwhile isolating the system microwave generator from the dc temperaturesignals. The use of a computer in the system controller to sense forwardpower, reflected power, measure the thermistor temperature, and possiblymonitor other variables such as monitoring tissue temperature by one ormore independently inserted temperature sensors, provides control andfeedback for the applied microwave power and the proper safety andoperation of the microwave coagulation or ablation procedure.

In addition to the temperature sensor to measure the approximatetemperature of the cooling fluid line in the applicator, one or moretemperature sensors may be placed along the elongate applicator body soas to place the one or more temperature sensors at positions to measurethe temperature of the tissue of the living body along the applicator.If such additional temperature sensors are provided, it is usuallyadvantageous to position one of such temperature sensors at a positionclose to an expected outer margin of the desired or allowable heatingarea in the living body tissue to be heated by the antenna duringoperation of the applicator. This can be used to provide a warning ifthe tissue to be protected outside the margin of the area to be treatedis approaching an undesirably high temperature. It can also be used toestimate the location of the outer margin of the effective heated volumeduring treatment.

The use of phased arrays can also reduce microwave heating along theshafts of the applicators due to cross coupling of the energy betweenthe antennas that are driven in phase and separated by a distance thatprovides for partial power cancellation along the outer portion of theinserted applicators and an increase in tissue heating between theseinserted applicators. This partial power cancellation is accomplishedwhen the distance between approximately parallel inserted antennas isapproximately a half of a wavelength so that the cross coupled energy issomewhat out of phase with that on an antenna due to its own radiatedenergy. For a frequency of 915 MHz, for example, the wavelength intypical high water content tissues such as muscle and tumors isapproximately 4.3 to 4.7 cm. This means that for an insertion separationof 2.1 to 2.4 cm the separation is about right for this 180 degreerelationship. There is also cross coupled phase cancelation forsignificant phase differences other than 180 degrees, for example, a 135or 225 degree phase difference will still provide partial phasecancellation from the cross coupling of the microwave coupled fields topartially cancel microwave energy along the outer portion of theinserted applicators. This would be consistent with an applicatorspacing of between about 1.6 to 3.0 cm for the 915 MHz example. Thispartial cancellation of microwave power around the inserted shaftsresults in reduced heating along the inserted shafts during activemicrowave tissue heating. This also reduces the local power fieldslocally around the radiating antennas and the outer shafts to reducetissue sticking to the antennas and shafts.

The control of the heating may further include the systematic use ofapplicators in phased arrays with optimization computational guidance inthe form of pretreatment planning to provide an ideal insertion patternand power and phase application to the array of applicators to produceand control improved uniformity of power deposition, temperatures,and/or coagulation of tissue throughout the tumor volume, andparticularly at the tumor margins. The treatment is thereby optimizedand controlled by the aid of a numerical calculation of either theplanned insertion pattern and number of antennas or the actual patternachieved as indicated by various non-invasive imaging processes such ascomputer tomography (CT), ultrasound, or magnetic resonance imaging(MRI). It also may be feasible to use such planning information toadjust power amplitude and phase of each of the inserted applicators asdirected by a computer-controlled system using the predicted powerpatterns from the computer numerical model.

In a phased array embodiment of the invention, a single microwavegenerator is used to provide the microwave power for all applicators.The generator will usually operate at 915 MHz, which is an emissionfrequency commonly licensed for medical applications. This singlegenerator is connected to a passive, non-switching, microwave impedancematched power splitter (divider) which is used to direct powersimultaneously to multiple ports that are connected to one or moremicrowave dipole antennas such as described for the above describedapplicators. This arrangement provides approximately equal powersimultaneously to each of the output connection ports. This arrangementalso provides equal phase output of the microwave energy at each of theoutput ports. Thus, when multiple antennas are connected to the ports ofthe power splitter, they have equal power and equal relative phase andare thus correctly called a phased array of antennas. The cables goingto the radiating points on each antenna are maintained at the sameelectrical length so that the radiated energy from the antennas arephase synchronous and phase coherent. Phase synchronous meaning thatthere is a fixed phase relationship between the radiation phase of allantennas and phase coherent meaning that the relative radiated phasefrom each antenna is approximately the same. The use of phased arrays asdescribed increases the heating in the spaces between the antennas byproviding improved uniformity of the coagulation of the targeted tissueproviding more power absorption than when using channel switching andother non-phase synchronous and non-simultaneous channel operationmethods.

When using a phased array of applicators, he applicator antennas areinserted in approximately a pattern than corresponds with equal spacingalong the circumference of an insertion circle around the tissue to betreated. This provides for approximately equal spacing between theantennas along the perimeter of an insertion pattern. Thus, a pattern oftwo antennas would be inserted at a distance of separation that wouldrepresent the diameter of an insertion circle. Three antennas would forma triangle pattern as they are approximately equally spaced around thecircumference of a circular insertion pattern. Four antennas would forma square pattern. The antennas should be approximately parallel asinserted with the central point of the radiation from each antennainserted to approximately the same depth position with respect to thetissue to be treated so as to have the radiation feedpointsapproximately aligned side by side.

As indicated, the applicator of the invention can be used as a singleapplicator inserted into the diseased tissue, or as an array of morethan one applicator positioned in or around the diseased tissue. Inorder to provide the most efficient transfer of microwave energy fromthe microwave generator to the tissue to be treated, the flow paths ofthe microwave energy from the microwave generator to the applicatorantennas should be impedance matched and tuned for the number ofapplicators used. This can require different systems with differentpower splitters when a single applicator is used or when multipleapplicators are used to form an array. The present invention can providea special power splitter circuit so that a single system can be used fora single applicator or for a plurality of applicators. According to theinvention, at least one power splitter circuit is provided for couplingthe microwave energy generator to at least one coaxial microwave energysupply cable for supplying microwave energy from the microwave generatorto the microwave applicator. The at least one power splitter circuit hasa microwave power input connected to the microwave generator and aplurality of output ports, wherein one of the plurality of output portsis a single connection output port for use where only a single coaxialmicrowave energy supply cable and microwave applicator is connected tothe power splitter circuit, and the remaining output ports of theplurality of output ports are multiple connection output ports for usewhere two or more coaxial microwave energy supply cables and microwaveapplicators are connected to two or more multiple connection outputports of the power splitter circuit. The single connection output portis impedance matched and tuned to provide efficient energy transfer whenusing a single applicator and the multiple connection outlet ports areimpedance matched and tuned to provide efficient energy transfer whenusing a number of applicators anywhere from two to the total number ofmultiple connection output ports provided. In this way, if a singleapplicator is used, it is connected to the single connection outputport. If multiple applicators are used, each of the multiple applicatorsis connected to a different multiple connection output port and nothingis connected to the single output port.

Means can be provided to detect whether or not there is an antennaconnected to a particular microwave power output port, and whether suchantenna is connected to a correct port. This can be done if thermistoror other resistive temperature sensors are used in the applicators, aspreviously described, and the substantially dc temperature sensorsignals are transmitted to the system controller through the coaxialpower supply cable. In such instance, the system controller can detectwhich of the output ports have applicators attached by detecting whethertemperature sensors signals are present at such output ports. Bydetecting the number of applicators attached to output ports of a powersplitter circuit and to which of the output ports they are attached, thesystem controller can determine if a single applicator is connected, andif so, whether it is properly connected to the single connection outputport, or whether two or more applicators are connected, and if so,whether they are all properly connected to multiple connection outputports. The system controller can provide an alarm signal if one ofmultiple applicators is attached to the single connection output port orif a single applicator is connected to one of the multiple output ports.

The design of a narrow separation gap between the conductive applicatorinsertion tip and the insertion end of the conductive outer sleeveprovides a zone of high microwave intensity at the gap which can be usedto coagulate tissues along the insertion track if the microwave power isapplied as the microwave antenna is withdrawn from the treated tissue.This provides coagulation of tissue and blood vessels that may be alongthe insertion track as well as any disease tissue that may be along thetrack as the applicator is removed from the tissue. By providingregularly spaced depth markings on the elongate applicator andwithdrawing the applicator from the living body in coordination withregular cadence sounds, a substantially constant rate of removal of theapplicator from a living body can be achieved for effective trackablation.

THE DRAWINGS

Other features of the invention will become more readily apparent fromthe following detailed description when read in conjunction with thedrawings in which the accompanying drawings show the best modescurrently contemplated for carrying out the invention, and wherein:

FIG. 1 is a side elevation of an applicator, in accordance with anembodiment of the present invention;

FIG. 2 is a vertical section of a portion of the applicator of FIG. 1;

FIG. 3 is a cut away perspective view of a portion of the applicator ofFIG. 2;

FIG. 4 is a vertical sectional of the handle portion of the applicatorof FIG. 1;

FIG. 5 is a circuit diagram of the electrical connections within thehandle portion of the applicator as shown in FIG. 4;

FIG. 6 is a perspective cut away view of another embodiment of handlefor the applicator of the invention

FIG. 7 is a block diagram of a system for microwave therapy using theapplicator of the invention;

FIG. 8 is a block diagram of a system of the invention for microwavetherapy using an array of applicators of the invention; and

FIG. 9 is a side elevation of the applicator shown in FIG. 1, showingadditional depth markings along the applicator.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made to the exemplary embodiments illustrated inthe drawings, and specific language will be used herein to describe thesame. It will nevertheless be understood that no limitation of the scopeof the invention is thereby intended. Alterations and furthermodifications of the inventive features illustrated herein, andadditional applications of the principles of the inventions asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the invention.

One embodiment of a microwave applicator of the invention for microwavecoagulation and ablation treatment of diseased tissue within living bodytissue is illustrated in FIG. 1. The applicator, referred to generallyas 10, includes a handle 12 from which a substantially rigid elongateapplicator body 14 extends with an insertion tip 16 forming theinsertion end portion of the applicator for insertion into a tissueregion of the living body. The substantially rigid elongate applicatorbody 14 includes an outer conductive sleeve 18 extending from the handle12, a conductive shunt 20, the conductive insertion tip 16, and adielectric collar 22 positioned between the insertion tip 16 and theshunt 20. The outside diameters of the exposed portions of the outerconductive sleeve 18, the conductive shunt 20, the dielectric collar 22,and the insertion tip 16 (which may be sharpened at its insertion end17), are all about equal so as to form a smooth continuous elongateapplicator body for insertion into the living body tissue. The elongateapplicator body may be coated with a stick resistent dielectric materialsuch as Teflon, not shown. A pistol grip 24 allows the handle to beeasily held for manipulation of the applicator.

The applicator has a microwave antenna portion 25 toward the insertiontip of the elongate applicator body 14 to radiate microwave energy fromthe antenna portion into the living body tissue. Microwave energy istransmitted from the handle 12 through the elongate applicator body tothe antenna portion by a coaxial microwave transmission line 26, FIGS.2-4, within the elongate applicator body and having an inner conductor29 and an outer conductor 27 separated by a dielectric material 28positioned therebetween. Although not required, the coaxial transmissionline 26 may be a semirigid coaxial cable with copper inner and outerconductors and a Teflon or Teflon and air dielectric material. No outerdielectric insulating material is used. Such coaxial cable will usuallyhave about a fifty ohm impedance which provides a good impedance matchto the microwave generator and to typical living body tissuecharacteristics.

The outer diameter of the coaxial transmission line (also the outerdiameter of the outer conductor 27 of the coaxial transmission line) issmaller than the inside diameter of the outer conductive sleeve 18 so aspace 82 is provided between the transmission line and the outerconductive sleeve. This space will be referred to as a cooling fluidspace. Conductive shunt 20 is positioned around and in electricalcontact with both the insertion end portion 83 of the transmission lineouter conductor 27, and the outer conductive sleeve 18. Shunt 20includes a reduced outer diameter end portion 84 toward the handle endof the applicator dimensioned to fit into the space 82 between theoutside surface of the outer conductor 27 of the coaxial transmissionline 26 and the inside surface of the outer conductive sleeve 18. Shunt20 can be soldered to both the outer conductor 27 and the outer sleeve18 to ensure good electrical connection. Soldering will also secureshunt 20 to outer sleeve 18 for a strong connection of shunt 20 tosleeve 18. However, shunt 20 can be secured to sleeve 18 and, ifdesired, to outer conductor 27, by a bonding agent, such as an epoxyadhesive material. If the bonding agent is conductive, it can replacesoldering. With this connection, shunt 20 closes or blocks cooling fluidspace 82 toward the insertion end 85 of the outer conductive sleeve 18.

Shunt 20 extends beyond the actual end 86 of the outer conductor to forman enlarged inside diameter shunt portion 87. The insertion end ofenlarged diameter shunt portion 87 can accept a reduced diametermounting portion 88 of the applicator tip 16 with dielectric collar 22thereon. Dielectric collar 22 fits over the reduced diameter mountingportion 88 of the applicator tip 16, and itself has a reduced diameterinsertion portion 89 that fits into enlarged inside diameter shuntportion 87. This interfitting arrangement produces a strong connectionof the tip to the remainder of the applicator, with the dielectriccollar 22 being bonded to the tip and the shunt by an adhesive materialsuch as epoxy.

Dielectric collar 22, being positioned between shunt 20 and tip 16,electrically insulates tip 16 from shunt 20. Since shunt 20 iselectrically connected to the outer conductor 27 of the coaxialtransmission line 26, shunt 20 becomes an extension of the outerconductor 27 and the insertion end 90 of the conductive shunt 20 becomesthe effective insertion end of the outer conductor 27. The innerconductor 29 of the coaxial transmission line extends toward theinsertion end of the applicator beyond the insertion end 91 of thecoaxial transmission line dielectric material 28 to an inner conductorinsertion end 92. However, both the insertion end 91 of the coaxialtransmission line dielectric material and the insertion end 92 of thecoaxial transmission line inner conductor are within the enlarged insidediameter shunt portion 87 of shunt 20 and do not extend beyond theinsertion end 90 of shunt 20.

The reduced diameter mounting portion 88 of applicator tip 16 alsoincludes a tip tab 93 extending therefrom toward the handle end of theapplicator and the insertion end 91 of the coaxial transmission linedielectric 28. The tip tab 93 is positioned so that the extension of thecoaxial transmission line inner conductor 29 beyond the end 91 of thecoaxial transmission line dielectric 28 is adjacent to and can besecured in electrical contact, such as by soldering, to the tip tab 93.With this arrangement, inner conductor 29 does not extend into tip 16,but is merely adjacent to and electrically connected to tip tab 93.

As constructed, the conductive outer sleeve 18 may be of a metalmaterial such as stainless steel, the conductive tip and the shunt maybe formed of a metal material such brass or stainless steel, and thedielectric insulating collar may be formed of a substantially rigidplastic material. All such parts may be bonded using an epoxy adhesive.Further, while the construction described for this illustratedembodiment provides an embodiment of a microwave antenna toward theinsertion end of the applicator, various other applicator constructionscan be used to form a microwave antenna toward the insertion end of theantenna and to form an insertion end of the applicator.

As shown in FIG. 1, elongate applicator body 14 extends from handle 12.As shown in FIG. 4, outer conductive sleeve 18 is secured in the forwardportion 13 of handle body 15 and in the forward end of cooling fluidreservoir 38, which cooling fluid reservoir 38 is mounted within handlebody 15. Cooling fluid reservoir 38 includes two reservoir chambers 34and 36 separated by guide sleeve 40 that extends from connection toreservoir partition 35 into outer conductive sleeve 18 and within outerconductive sleeve 18 toward the insertion end of the applicator. Theguide sleeve 40 may be a thin walled plastic sleeve made of polyimideplastic such as Kapton. Attachment of the outer conductive sleeve 18 tohandle body 15 and fluid reservoir 38, and attachment of guide sleeve 40to reservoir partition 35, may be with glue, epoxy, or other bondingagent. Coaxial transmission line 26 extends through cooling fluidreservoir 38 and into guide sleeve 40. Coaxial transmission line 26extends through the entire length of guide sleeve 40 and beyond theguide sleeve insertion end 41, FIG. 2, and into shunt 20.

As seen in FIGS. 2 and 4, guide sleeve 40 extends into cooling fluidspace 82 between the outside of coaxial transmission line 26 and theinside of outer conductive sleeve 18. Guide sleeve 40 divides coolingfluid space 82 into an inner cooling fluid space 42 and an outer coolingfluid space 43 along the length of guide sleeve 40 in space 82 Innercooling fluid space 42 is formed between the outside surface of coaxialtransmission line 26 and the inside surface of guide sleeve 40 and outercooling fluid space 43 is formed between the outside surface of guidesleeve 40 and the inside surface of outer conductive sleeve 18.Reservoir chamber 34 communicates with inner cooling fluid space 42 andreservoir chamber 36 communicates with outer cooling fluid space 43.

While either reservoir chamber 34 or 36 could be a cooling fluid inletor cooling fluid outlet, it has been found for ease of placement of thetemperature sensor, as will be explained in respect of the location oftemperature sensor 60, that reservoir chamber 34 can be the coolingfluid inlet reservoir and reservoir chamber 36 can be the cooling fluidoutlet reservoir. In such instance, cooling fluid to the applicator willflow from a source of cooling fluid, not shown, through tubing 30 intoreservoir chamber 34. From reservoir chamber 34, cooling fluid flowsthrough inner cooling fluid space 42 along the outside surface ofcoaxial transmission line 26 to cool the outside surface of coaxialtransmission line 26. As previously indicated in regard to FIG. 2,cooling fluid space 82 into which guide sleeve 40 extends is blocked atthe insertion end portion of outer conductive sleeve 18 by the reduceddiameter portion 84 of shunt 20 which fits into and blocks the insertionend of space 82. As seen in FIG. 2, the insertion end 41 of guide sleeve40 ends before reaching the end of space 82 created by shunt 20 so as toleave an undivided fluid space portion which connects the inner coolingfluid space 42 and the outer cooling fluid space 43. Thus, as coolingfluid flowing in inner cooling fluid space 42 toward the insertion endof the applicator reaches the insertion end 4 l of guide sleeve 40, itflows into the undivided space 82 around the insertion end 41 of guidesleeve 40 into outer cooling fluid space 43 and flows along the insidesurface of outer conductive sleeve 18 back into reservoir chamber 36 andout fluid outlet tube 32 back to the fluid supply to be cooled andrecirculated or to a fluid drain.

As shown in FIG. 4, microwave energy is provided to the applicator froma microwave generator, not shown, by a coaxial microwave energy supplycable 46 that provides a path for the microwave energy from thegenerator to the applicator. The coaxial microwave energy supply cable46 is typically a flexible fifty ohm coaxial cable containing an inneror center conductor 48, an outer conductor 49, and a dielectric spacer50 therebetween. In the illustrated embodiment, the connection betweenthe flexible coaxial microwave energy supply cable 46 and the semi-rigidcoaxial transmission line 26 is provided through a coupling circuit on aprinted circuit card 58 which supports small chip capacitors and aresistor, (see also FIG. 5 which is a circuit diagram of the circuitryof FIG. 4). The coaxial microwave energy supply cable center conductor48 is connected by conductive metal path 51 on the circuit card 58 tocapacitor 52 which is connected to inner conductor 29 of coaxialtransmission line 26. The coaxial microwave energy supply cable outerconductor 49 is connected by conductive element or wire 47 to conductivemetal path 53 on the circuit card 58 which is connected to outerconductor 27 of coaxial transmission line 26. This provides a directpath for the microwave currents to flow between the outer conductors.Circuit diagram FIG. 5 shows a capacitor 55 connected between the twoouter conductors 49 and 27 which is not necessary and not shown in FIG.4, but may be advantageous to include to provide further isolation ofthe microwave antenna from dc currents in the flexible coaxial microwaveenergy supply cable 46.

A temperature sensor in the form of a thermistor 60 is placed over theouter conductive sleeve 18 and bonded to it so that it is approximatelythe same temperature as the outer conductive sleeve 18. Thermistor 60,when placed at the location shown in FIG. 4, measures the temperature ofouter conductive sleeve 18 at about its handle end, which will be atapproximately the temperature of the cooling fluid after flowing throughthe elongate applicator body 14. Thermistor 60 can be located at otherlocations that enable it to indicate the approximate temperature of thecooling fluid after or during flow through the applicator. When locatedas shown, thermistor 60 measures the approximate temperature of thecooling fluid between guide sleeve 40 and the outer conductive sleeve 18as the cooling fluid returns to the cooling fluid outlet reservoirchamber 36 after flowing through inner and outer cooling fluid spaces 42and 43. The cooling fluid at this location will have reachedapproximately its highest temperature. Thermistor 60 could be located inthe cooling fluid itself, if desired, such as in cooling fluid outletreservoir chamber 36. The function of this thermistor 60 is to providean indication that the cooling fluid is actually flowing inside theapplicator whenever the microwave power is applied. During theapplication of microwave energy, the microwave energy causes selfheating of the coaxial transmission line 26 in the applicator. Thisincreases the temperature of coaxial transmission line 26 therebyheating the surrounding parts between thermistor 60 and coaxialtransmission line 26. Without circulation of cooling fluid, applicatorouter conductive sleeve 18 can reach temperatures that can damage normaltissue. The flow of cooling fluid inside the applicator along coaxialtransmission line 26 and outer conductive sleeve 18 removes much of thatgenerated heat so that thermistor 60 remain cooler when the coolingfluid is flowing than if there is no fluid flow. If fluid flow stops oris restricted, the fluid will heat to a higher temperature than whenproperly flowing. When properly flowing, the applicator outer conductivesleeve 18 will remain below tissue damaging temperatures.

A thermisitor is a resistive electrical device that varies itsresistance depending upon its temperature. The two wires 62 a and 62 bfrom thermistor 60 are connected across capacitor 56. Wire 62 a connectsto capacitor 56 and also connects directly to outer conductor 49 of theflexible coaxial cable 46. Wire 62 b attaches to the opposite side ofcapacitor 56 and also to one side of resistor 54 through conductivemetal path 57. The other side of resistor 54 connects to conductivemetal path 51 via a wire or conductive metal path 59. Thus, thermistor60 is connected electrically between inner conductor 48 and outerconductor 49 of flexible coaxial cable 46. This enables the resistanceof the thermistor 60 to be monitored by a direct electrical current thatis passed from the center conductor 48 through conductive metal traces51 and 59 to resistor 54 and conductive metal trace 57 and wire 62 b tothermistor 60 and back via wire 62 a and wire 47 to the outer conductor49 of flexible coaxial cable 46. Capacitor 52 prevents the directelectrical current from flowing into inner conductor 29 of coaxialtransmission line 26 and therefore prevents the direct electricalcurrent from flowing into the applicator antenna and living body intowhich the applicator is inserted. If capacitor 55 is provided in thecircuit, it prevents the direct electrical current from flowing into theouter conductor 27 of coaxial transmission line 26 to further ensurethat direct electrical current does not flow into the antenna and intothe living body into which the applicator is inserted. This describedcircuitry allows the flexible coaxial microwave energy supply cable toserve a dual purpose. The dc current for monitoring of the resistance ofthermister 60 passes through the flexible coaxial microwave energysupply cable 46 along with the microwave energy that flows through theflexible coaxial microwave energy supply cable 46 from the microwaveenergy generator to the applicator. With the arrangement described, thetemperature indicating signal is carried between the thermistor and thesystem controller over the same two coaxial cable conductors 48 and 49that carry the microwave power from the microwave generator to theapplicator. This eliminates the need for separate additional wires fromthe handle to the system controller to carry the temperature signalsfrom the thermistor.

As indicated, the signal from the thermistor 60 provides an indicationto the system controller of the temperature of the outer conductivesleeve and the cooling fluid circulating in the applicator. With themicrowave power applied to the applicator, which results in heating ofcoaxial transmission line 26, as long as cooling fluid is properlyflowing in the applicator, the temperature of thermistor 60 will remainlow. If the cooling fluid stops flowing in the applicator or flow isrestricted for some reason, the coaxial transmission line 26 will beginto heat and the temperature of outer conductive sleeve 18 and of anynon-flowing or slowly flowing fluid in the applicator will alsoincrease. This increases the temperature of thermistor 60. This increasein measured temperature of thermistor 60 provides an indication thatcooling fluid is not flowing properly and the system controller canactivate an alarm or activate other corrective action.

FIG. 6 shows a cut away perspective view of a handle similar to that ofFIG. 4, but with a slightly different configuration of handle body 45and different orientation of inlet 30 and outlet 32 tubes from reservoirchambers 34 and 36. However, the configuration of the handle componentsis substantially the same and components are numbered the same as inFIG. 4. The wires from the thermistor 40 are not shown. FIG. 6 gives abetter illustration of the actual construction of the applicator handle.

As can be appreciated from the above explanation, in addition toproviding a means by which the applicator can be held and manipulatedfor insertion into the living body, handle 12 serves as an interfacebetween the substantial rigid elongate applicator body 14 and theflexible coaxial microwave energy supply cable extending from themicrowave generator to the applicator, provides for the insertion of thetemperature signals onto the flexible coaxial microwave energy supplycable, and serves as an interface between the flexible fluid hoses fromand to a source of cooling fluid and the cooling fluid reservoir. Whilethe flexible coaxial microwave energy supply cable and the flexiblefluid hoses are shown extending from the end of the handle grip (andcould be enclosed in a sheath, if desired), connectors could be providedon the handle so that the flexible coaxial microwave energy supply cablecould be connected to and disconnected from the handle and so that theflexible fluid hoses could also be connected to and disconnected fromthe handle. Further, various configurations of handles can be used.

FIG. 7 is a functional block diagram of a basic system of the inventionas described above using a single applicator for patient treatment. Anoperator interface 61, such as a computer screen and keyboard or asimple touch screen, is provided for display and monitoring of thesystem controls and the treatment procedures. The user interface isconnected to a system controller 64, such as a computer processor, by acable 63. The controller provides control and monitoring to a microwavegenerator 68 through a cable 66. The generator 68 has a microwaveoscillator where the power amplitude can be controlled and monitored bythe controller 64 including the measurement of both the forward andreflected power at the output of the generator 68. The generatedmicrowave power is then directed to a multiplexer and power splittercircuit 74 by a transmission line cable 70, such as a coaxial cable. Themicrowave path inside the multiplexer and power splitter circuit 74contains an impedance matched microwave path directing the microwavepower to the applicator 10 with elongate applicator body 14 by aflexible coaxial microwave energy supply cable 72. As described, withinthe applicator 10 there is a dc current path that flows through atemperature sensing thermistor that enables a direct current to alsoflow through the coaxial microwave energy supply cable 72. This directcurrent that is used to measure the temperature within the applicatorelongate body 14 is separated from the microwave power signal in themultiplexer portion of the multiplexer and power splitter circuit 74 andis sent along a dc circuit path 76 that is directed to a temperaturemonitoring circuit 78. The temperature monitoring circuit 78 thendirects a temperature signal back to the controller 64 through a cable80 to enable the controller to monitor and control microwave powerlevels generated by microwave generator 68 to limit the microwave powertransmitted to the applicator if excessive temperatures are measured inthe applicator 10. Temperature monitoring circuit 78 may be part of thecontroller 64.

In many instances, it will be desired to provide patient treatment usinga phased array of applicators rather than a single applicator. Whenusing a phased array, a plurality of applicators are inserted into thepatient in approximately parallel orientation in a pattern approximatelyevenly spaced apart along the circumference of an insertion circlearound the tissue to be treated. Each applicator should be inserted sothat the radiating antenna is at approximately the same depth positionwith respect to the tissue to be treated so as to have the radiationfeedpoints approximately aligned side by side. The use of multipleapplicators in phased arrays generally allows better control of theapplicators to produce better uniformity of power deposition,temperature, and/or coagulation of tissue throughout a tumor volume tobe treated and particularly at the tumor margins than when using asingle applicator. The use of phased arrays can also reduce microwaveheating along the shafts of the applicators due to cross coupling of theenergy between the antennas that are driven in phase and separated by adistance that provides for partial power cancellation along the outerportion of the inserted applicators and an increase in tissue heatingbetween these inserted applicators. With phased arrays, pretreatmentplanning can be used to provide an ideal insertion pattern and power andphase application to the array of applicators to produce and control thedesired heating. The treatment is thereby optimized and controlled bythe aid of a numerical calculation of either the planned insertionpattern and number of antennas or the actual pattern achieved asindicated by various non-invasive imaging processes such as computertomography (CT), ultrasound, or magnetic resonance imaging (MRI). Poweramplitude and phase of each of the inserted applicators can be adjustedas directed by a computer-controlled system using the predicted powerpatterns from the computer numerical model. Further, actual temperaturemeasurements can be taken and compared with the predicted power patternsand predicted temperatures and the system controlled to compensate fordifferences.

In a phased array embodiment of the invention, a single microwavegenerator is used to provide the microwave power for all applicators.The generator will usually operate at 915 MHz, which is an emissionfrequency commonly licensed for medical applications. This singlegenerator is connected to a passive, non-switching, microwave impedancematched power splitter (divider) which is used to direct powersimultaneously to multiple ports that are connected to one or moremicrowave dipole antenna such as described for the above describedapplicators. This arrangement provides approximately equal powersimultaneously to each of the output connection ports. This arrangementalso provides equal phase output of the microwave energy at each of theoutput ports. Thus, when multiple antennas are connected to the ports ofthe power splitter, they have equal power and equal relative phase andare thus correctly called a phased array of antennas. The cables goingto the radiating points on each antenna are maintained at the sameelectrical length so that the radiated energy from the antennas arephase synchronous and phase coherent. Phase synchronous meaning thatthere is a fixed phase relationship between the radiation phase of allantennas and phase coherent meaning that the relative radiated phasefrom each antenna is approximately the same. Since different arraypatterns are desirable for different optimized treatments, and desiredtreatments can use a single applicator or varying numbers of multipleapplicators, it is desirable to have a system which can power andmonitor a single applicator or a multiple number of applicators.However, present systems are usually designed to optimize power deliveryto either a single applicator or to a set number of multipleapplicators. This does not provide the flexibility desired to configuredifferent arrays using a single delivery system. It would also bedesirable in array power systems to have an indication as to whether ornot there is an antenna connected to a particular microwave power outputport and an indication as to whether antennas are correctly connected.

FIG. 8 shows an embodiment of a multiplexer and power splitter circuitaccording to the invention that provides for the separation oftemperature signals from microwave power signals for a plurality ofapplicators and which can provide optimization for attachment of asingle applicator, two applicators, or three applicators. Microwavepower signals from a microwave generator, not shown, are supplied to themultiplexer and power splitter circuit through coaxial cable 100,generally of fifty ohm impedance. The multiplexer and power splittercircuit is generally on a printed circuit card made of low lossdielectric material such as Teflon based material with a ground plane onone side and the circuit show in FIG. 8 that represents the conductivepaths forming various transmission lines on the other side. The inputmicrowave power signal connects to an input in the form of a conductivepatch 102 that provides a power splitting section. This directsmicrowave power to four paths, one path shown by path 104, and threeidentical paths shown by paths 114. Along path 104 is a chip typecapacitor 106 that conducts microwave power but blocks direct current toprevent direct current from reaching power splitting patch 102. Theinput microwave power flows through capacitor 106 to circuit output port110 along transmission line 108. The transmission lines 104 and 108 arefifty ohm transmission lines which together have an electrical lengthdelay of one hundred eighty degrees at the microwave operatingfrequency. Capacitor 106 has a low impedance of typically less than twoohms reactive impedance to avoid mismatching the transmission line. Thisthen directs microwave power from the input transmission line 100 to thecircuit output port 110. Output port 110 forms an output port forconnection of a single applicator antenna through a fifty ohm impedancecoaxial microwave energy supply cable attached to output port 110. Thisoutput port 110 is used if only a single antenna is to be connected tothe multiplexer and power splitter circuit, and is sometimes referred toherein as a single connection output port.

Power splitter conductive patch 102 is also connected to three identicalother transmission lines having microwave input sections 114 each with aseries chip capacitor 112 along the path, and microwave output sections116. Similarly to capacitor 106, each capacitor 112 in the microwaveinput section has a low impedance of typically less than two ohmsreactive impedance to allow microwave power to pass but block directcurrent flow to prevent direct current from reaching power splittingpatch 102. The overall length of the microwave input section of thetransmission lines from the power splitter conductive patch 102 throughthe capacitor 112 along path 114 is approximately ninety degrees delayat the microwave frequency. Also the characteristic impedance of themicrowave input section of the transmission lines 114 with capacitors112 of typically between seventy and ninety ohms from the power splitterconductive patch 102 to the end of path 114 is used to provide animpedance matching section for the input when two or three applicatorsare connected to the multiple connection output ports 118. The microwaveoutput sections 116 are fifty ohm sections that connect the lines 114 tothe multiple connection output ports 118 and these microwave outputsections 116 are typically the length to delay the microwave signalapproximately ninety degree. The fifty ohm impedance of the microwaveoutput sections 116 provide impedance matching for the flexible coaxialmicrowave energy supply cables and the applicators connected to theoutput ports 118.

The described power splitter circuit forms an impedance matchedmicrowave power splitter that when a single applicator is to be used italone is connected to the single connection output to port 110. Whenthis is the case the other three output ports, each a multipleconnection output port 118, are not connected to an applicator. The pathlength from the power splitter conductive patch 102 to each of thesemultiple connection output ports 118 is one hundred eighty degrees. Themicrowave power that travels to these multiple connection output ports118 is reflected completely back when there is no connection to theports and this reflected power is reflected with the same phase angle asthe incoming power to these ports because this is an open circuittermination. This means that the overall phase delay of the power fromthe power splitter conductive patch 102 to the multiple connectionoutput ports 118 and back to the power splitter conductive patch 102 isthree-hundred-sixty degrees. This unique phase delay then appears to thepower splitter as an open circuit. Thus, the open ports 118 turn thesepaths into tuning paths that do not reflect power that would reach theinput line 100, but would direct the full power only to singleconnection output port 110 to the single applicator that is connected tooutput port 110 for efficient power transfer to the single applicator.

When two or three applicators are connected to respective multipleconnection output ports 118, there will be no applicator connected tothe port 110. The path delay between the power splitter conductive patch102 and the output port 110 is also one-hundred-eighty degrees.Therefore, the delay to the output port 110 and back to the conductivepatch 102 is three-hundred-sixty degrees. When there is no applicatorattached to the single connection output port 110 it also turns into atuning path for the microwave energy. The result is that the microwavemultiplexer and power splitter circuit is an impedance matched splitterwhich automatically allows the power to be directed to the connection of1, 2, or 3 applicators. It would not be permitted to attach only asingle applicator to one of the multiple connection output ports 118because it would result in an impedance mismatch and would causeunacceptable reflected power to the input line 100. Also, if noapplicators are connected to any of the ports of the power splittercircuit, all transmission paths appear as open circuits. This allowsmultiple power splitter circuits to be use to provide for more thanthree applicators when desired. For example, if two power splittercircuits are used anywhere between one and six applicators can beconnected to the system.

The multiplexer and power splitter circuit also includes an inductivecoil or choke 120, 122, 124, and 128 connected to each of thetransmission lines 104 and 114. Each of these inductive coils isconnected through a capacitance to the ground chassis with capacitors128, 130, 132, and 134, respectively. These capacitors and the inductivecoils filter the microwave signals from the temperature sensing ports136, 138, 140, and 142, but pass direct current signals from thetransmission lines 108 and 114 to these temperature sensing ports. Thesetemperature sensing ports are connected to temperature monitoringcircuitry and then to the system computer or controller for detection ofthe measured resistance of the thermistors that are connected to the twowire coaxial microwave energy supply connectors of the applicators aspreviously described. These direct current temperature sensing signalsfrom the applicators to the temperature sensing ports provide ameasurement to the system controller of the temperature measured by thetemperature sensors in each of the applicators.

These direct current temperature sensing signals from the applicators tothe temperature sensing ports also provide a measurement to the systemcontroller of whether applicators are connected to particular outputports of the multiplexer and power splitter circuit. If an applicator isconnected to a particular multiplexer and power splitter circuit outputport, for example to output port 110, a temperature signal will bepresent on temperature sensing port 136. The system controller will thenknow that an applicator is connected to output port 110. Similarly, if atemperature signal is present on temperature sensing ports 138 and 142,the system controller will know that two applicators are connected totwo of the multiple connection output ports 118 and will be able toidentify which of the two output ports have applicators connectedthereto. If the system controller senses temperature signals ontemperature sensing ports 136 and 138, the system controller knows thatthere are two applicators connected to the multiplexer and powersplitter circuit, but that the applicators are not properly connectedsince one of the two applicators is improperly connected to singleconnection output port 110 while the other of the two applicators isproperly connected to one of the multiple connection output port 118.The system controller can then provide a warning signal to a system userindicating that the applicators are improperly connected, and that theapplicator connected to the single connection output port 110 should bedisconnected and connected to one of the multiple connection outputports 118. The use of this special multiplexer and power splittercircuit, in addition to providing an indication that the proper numberof applicators are connected to the correct output ports for efficientand desired microwave power delivery to the connected applicators, alsoenables the measurement of applicator cooling temperature to determinethat fluid is properly flowing in each of the connected applicators toprotect the normal body tissues.

If temperature sensing is not required, but the sensing of theattachment of microwave applicators to power splitter circuits isdesired, the thermistor or other temperature sensors that provide directcurrent temperature signals can be replaced with regular resistors whichwill provide substantially dc signals in the manner of thermistor toindicate that microwave applicators are attached to a power splitteroutput port and indicate to which port or ports the applicators areattached. This use of resistor will be considered equivalents of thethermistors or other temperaturs sensors that provide direct currenttemperature sensor signals for the purposes of the applicator detection.

In many cases, it is desirable to keep the microwave power on to theapplicator as the applicator is withdrawn from the treatment site in thebody when treatment of the diseased tissue is completed. This isbecause, in some instances, diseased tissue from the treatment site maybe left along the insertion and withdrawal track which can seedadditional diseased tissue growth. Further, in many body locations,removal of the applicator leaves an open wound along the insertion trackwhich will bleed. Application of heat as the applicator is withdrawnprovides coagulation of tissue and blood vessels that may preventbleeding along the insertion track. during withdrawal of the applicatorfrom the treatment site. As shown in FIG. 9, a narrow separation gap 22between the conductive applicator insertion tip 16 and the effectiveinsertion end of the outer conductive sleeve 18, which is the insertionend of the shunt 20, provides a zone of high microwave intensity at thegap which can be effectively used to coagulate tissues along theinsertion track if the microwave power is applied as the microwaveantenna is withdrawn from the treated tissue. While methods of stepwisetrack ablation are known where the applicator is withdrawn in steps withmicrowave ablation heating performed at each step, and while it is knownthat track ablation can be performed with a continuous withdrawal of theapplicator, effective continuous track ablation requires a substantiallycontrolled constant preset withdrawal rate for the applicator. This isdifficult to obtain when withdrawing an applicator.

As shown in FIG. 9, the applicator of the invention can be provided withdepth marking 150 visible on the outside of the elongate applicator bodyat regular intervals along the elongate applicator body. The purpose ofthese markings is to provide an indication as to the depth of applicatorpenetration into the living body, and such markings are regularlyspaced, such as every centimeter, along a portion of the length of theelongate applicator body where marks can be used to indicate depth ofpenetration. It has been found that these regularly spaced depthmarkings along the inserted shaft can be used to guide the rate ofwithdrawal of an applicator to provide effective coagulation of theinsertion track. For this process, the system includes a sound generatorthat can generate a regular cadence sound. The sound generator may, forexample, be part of the controller. By coordinating the cadence soundswith the amount of withdrawal of the applicator as indicated by thedepth markings that appear as the applicator is withdrawn, the propersteady rate of withdrawal of the applicator can be obtained to assureuniform coagulation of tissues along inserted track. A typical desiredrate of withdrawal of an applicator of the invention is approximatelyfive mm per second at a sixty watt power level. So, for example, if thedepth markings are spaced one cm apart along the inserted shaft, with acadence that provides an audible signal, such as a beep, every second,the cadence sound provides a guide for the withdrawal at a rate of fivemm for each audible beeping sound. This provides a rate of one cm everytwo seconds (every two beeps) to assure uniform coagulation of tissuesduring the withdrawal to reduce bleeding along the inserted track. Thismeans that the applicator is withdrawn so that a depth mark appearsevery two beeps.

Whereas the invention is here illustrated and described with referenceto embodiments thereof presently contemplated as the best mode ofcarrying out the invention in actual practice, it is to be understoodthat various changes may be made in adapting the invention to differentembodiments without departing from the broader inventive conceptsdisclosed herein and comprehended by the claims that follow.

1. A microwave applicator for insertion into living body tissue for heattreatment of diseased tissue within the living body tissue, themicrowave applicator comprising: an elongate applicator body having aninsertion end for insertion into a tissue region of the living body andan attachment end for attachment to a source of microwave energy; anantenna for radiating microwave energy disposed toward the insertion endof the elongate applicator body; a microwave energy transmission linedisposed within the elongate applicator body to conduct microwave energyfrom the attachment end of the applicator to the antenna, said microwaveenergy transmission line having an outside surface and an innerconductor and an outer conductor; an outer conductive sleeve extendingaround and spaced from the outside surface of the microwave energytransmission line to form an outside of a portion of the elongateapplicator body and to provide a cooling fluid space between the outsidesurface of the microwave transmission line and an inside surface of theouter conductive sleeve; a guide sleeve positioned concentrically aroundand spaced from the outside surface of the microwave energy transmissionline and the inside surface of the outer conductive sleeve to divide atleast a portion of the cooling fluid space into an inner cooling fluidspace along the outside surface of the microwave energy transmissionline and an outer cooling fluid space along the inside surface of theouter conductive sleeve, said inner cooling fluid space communicatingwith said outer cooling fluid space whereby said guide sleeve is adaptedto guide flow of a cooling fluid within the cooling fluid space to coolthe microwave energy transmission line and the outer conductive sleeve;a temperature sensor positioned to measure the approximate temperatureof a cooling fluid when a cooling fluid is present in the cooling fluidspace during operation of the applicator; a conductive applicator tipforming the insertion end of the applicator body and electricallycoupled to the inner conductor of the transmission line; and dielectricmaterial positioned between the conductive sleeve and the conductive tipto electrically insulate the conductive tip from the conductive sleeve.2. A microwave applicator for insertion into living body tissueaccording to claim 1, wherein the cooling fluid space terminates alongthe length of the microwave energy transmission line prior to reachingthe antenna.
 3. A microwave applicator for insertion into living bodytissue according to claim 2, additionally including a handle from whichthe outer conductive sleeve, microwave energy transmission line with theantenna toward the insertion end thereof away from the handle, and theguide sleeve extend for insertion into the living body.
 4. A microwaveapplicator for insertion into living body tissue according to claim 3,wherein the handle includes an inlet for connection to a source ofcooling fluid and an outlet for outflow of cooling fluid, and wherein,when cooling fluid is supplied through the cooling fluid inlet, thecooling fluid flows into the cooling fluid space in the elongateapplicator body from the handle and returns from the cooling fluid spacein the elongate applicator body into the handle.
 5. A microwaveapplicator for insertion into living body tissue according to claim 4,wherein the cooling fluid flows from the handle into the inner coolingfluid space and returns to the handle through the outer cooling fluidspace.
 6. A microwave applicator for insertion into living body tissueaccording to claim 4, wherein the cooling fluid flows from the handleinto the outer cooling fluid space and returns to the handle through theinner cooling fluid space.
 7. A microwave applicator for insertion intoliving body tissue according to claim 4, wherein the guide sleeveextending from the handle terminates in the cooling fluid space towardthe insertion end of the applicator before termination of the coolingfluid space along the length of the microwave energy transmission lineto thereby form an undivided cooling fluid space along the length of themicrowave energy transmission line between the termination of the guidesleeve and the termination of the cooling space, wherein the inner andouter cooling fluid spaces communicate through the undivided coolingfluid space.
 8. A microwave applicator for insertion into living bodytissue according to claim 7, wherein the temperature sensor is locatedin the handle to measure the approximate temperature of the coolingfluid returning to the handle.
 9. A microwave applicator for insertioninto living body tissue according to claim 8, wherein the temperaturesensor is positioned against the outside of the outer conductive sleeveto measure the temperature of the outer conductive sleeve, whichtemperature approximates the temperature of the cooling fluid adjacentthe inside surface of the outer conductive sleeve at the position of thetemperature sensor.
 10. A microwave applicator for insertion into livingbody tissue according to claim 8, additionally including a coaxialmicrowave energy supply cable coupled to the microwave energytransmission line within the handle for connecting the microwave energytransmission line to a source of microwave energy.
 11. A microwaveapplicator for insertion into living body tissue according to claim 10,wherein the coaxial microwave energy supply cable is coupled to themicrowave energy transmission line through an applicator microwavecoupling circuit and wherein the applicator microwave coupling circuitadditionally couples the temperature sensor to the coaxial microwaveenergy supply cable whereby temperature sensor signals are transmittedalong the coaxial microwave energy supply cable with the microwaveenergy.
 12. A microwave applicator for insertion into living body tissueaccording to claim 11, wherein the temperature sensor is a thermistorand the temperature sensor signals are substantially dc signals.
 13. Amicrowave applicator for insertion into living body tissue according toclaim 11, additionally including a conductive shunt positioned along thelength of the elongate applicator between the outer conductive sleeveand the dielectric material and joining the dielectric material and theconductive applicator tip to the outer conductive sleeve, the connectionof the conductive shunt to the outer conductive sleeve forming the endof the cooling fluid space toward the insertion end of the applicator,and wherein the conductive shunt electrically couples the outerconductive sleeve to the outer conductor of the coaxial microwavetransmission line.
 14. A microwave applicator for insertion into livingbody tissue according to claim 8, wherein the guide sleeve is formed ofa nonconductive plastic material.
 15. A microwave applicator forinsertion into living body tissue according to claim 1, additionallyincluding a coaxial microwave energy supply cable coupled to themicrowave energy transmission line for connecting the microwave energytransmission line to a source of microwave energy.
 16. A microwaveapplicator for insertion into living body tissue according to claim 15,wherein the coaxial microwave energy supply cable is coupled to themicrowave energy transmission line through an applicator microwavecoupling circuit and wherein the applicator microwave coupling circuitadditionally couples the temperature sensor to the coaxial microwaveenergy supply cable whereby temperature sensor signals are transmittedalong the coaxial microwave energy supply cable with the microwaveenergy.
 17. A microwave applicator for insertion into living body tissueaccording to claim 16, wherein the temperature sensor is a thermistorand the temperature sensor signals are substantially dc signals.
 18. Amicrowave applicator for insertion into living body tissue according toclaim 1, wherein the guide sleeve is formed of a nonconductive plasticmaterial.
 19. A microwave applicator for insertion into living bodytissue according to claim 1, additionally including a conductive shuntpositioned along the length of the elongate applicator between the outerconductive sleeve and the dielectric material and joining the dielectricmaterial and the conductive applicator tip to the outer conductivesleeve, the connection of the conductive shunt to the outer conductivesleeve forming an end of the cooling fluid space toward the insertionend of the applicator, and wherein the conductive shunt electricallycouples the outer conductive sleeve to the outer conductor of thecoaxial microwave transmission line.
 20. A system for microwave therapyfor heat treatment of diseased tissue within a living body, the systemcomprising: a) a microwave generator for outputting microwave energy; b)a coaxial microwave energy supply cable coupled to the microwavegenerator for supplying microwave energy from the microwave generator toa microwave applicator; c) a microwave applicator comprising: i) anelongate applicator body having an insertion end for insertion into atissue region of the living body and an attachment end for attachment tothe coaxial microwave energy supply cable; ii) an antenna for radiatingmicrowave energy disposed toward the insertion end of the applicatorbody; iii) a microwave energy transmission line disposed within theelongate applicator body to conduct microwave energy from the attachmentend of the applicator to the antenna, said microwave energy transmissionline having an outside surface and an inner conductor and an outerconductor; iv) a temperature sensor adapted to produce temperaturesensor signals indicative of the temperature sensed by the temperaturesensor; and v) a coupling circuit coupling the temperature sensor to themicrowave energy supply cable and adapted to separate and combinetemperature sensor signals from and with microwave energy wherebytemperature sensor signals are transmitted along the coaxial microwaveenergy supply cable with the microwave energy; d) a system controllercoupled to the microwave generator and adapted to adjust output of themicrowave energy generator in response to temperature sensor signals toprevent the temperature sensed by the temperature sensor from exceedinga maximum allowable temperature; and e) a multiplexer circuit forcoupling the controller to the microwave energy supply cable and adaptedto separate and combine temperature sensor signals from and withmicrowave energy whereby temperature sensor signals transmitted alongthe microwave energy supply cable with the microwave energy are directedto and from the system controller.
 21. A system for microwave therapyfor heat treatment of diseased tissue within a living body according toclaim 20, wherein one or more microwave applicators are positioned inthe living body and wherein the multiplexer circuit is also a microwavepower splitter circuit having a microwave power input connected to themicrowave generator and a plurality of output ports adapted to beconnected to applicators through coaxial microwave energy supply cables,wherein one of the plurality of output ports is a single connectionoutput port for use where only a single microwave applicator isconnected to the multiplexer and power splitter circuit, and theremaining output ports of the plurality of output ports are multipleconnection output ports for use where two or more microwave applicatorsare connected to two or more multiple connection output ports of themultiplexer and power splitter circuit, and wherein the singleconnection output port is impedance matched and tuned to provideefficient energy transfer when using a single applicator and themultiple connection outlet ports are impedance matched and tuned toprovide efficient energy transfer when using a number of applicatorsanywhere from two to the total number of multiple output ports provided.22. A system for microwave therapy for heat treatment of diseased tissuewithin a living body according to claim 21, wherein the multiplexer andpower splitter circuit includes one single connection output port andthree multiple connection output ports to allow attachment of a singleapplicator to the one single connection output port, two applicators totwo of the multiple connection output ports, or three applicators tothree of the multiple connection output ports of the multiplexer andpower splitter circuit to provide one, two, or three applicatorsconnected to the multiplexer and power splitter circuit.
 23. A systemfor microwave therapy for heat treatment of diseased tissue within aliving body according to claim 22, wherein the impedance through themultiplexer and power splitter circuit for the single connection outputport is about fifty ohms with an electrical length delay of about onehundred eighty degrees, and the impedance through the multiplexer andpower splitter circuit for each of the three multiple connection outputports is configured in two sections, a microwave input section having animpedance of between about seventy and ninety ohms with an electricallength delay of about ninety degrees, and a microwave output sectionhaving an impedance of about fifty ohms with an electrical length delayof about ninety degrees.
 24. A system for microwave therapy for heattreatment of diseased tissue within a living body according to claim 22,wherein the system includes a plurality of multiplexer and powersplitter circuits connected to the microwave generator to provide morethan three applicators to the system.
 25. A system for microwave therapyfor heat treatment of diseased tissue within a living body according toclaim 21, wherein the multiplexer and power splitter circuit separatestemperature sensor signals from microwave energy for each output portwhereby temperature sensor signals transmitted along the microwaveenergy supply cable with the microwave energy for each applicatorconnected to an output port are directed separately to the systemcontroller, and wherein the system controller is programmed to determineto which output ports an applicator is connected, receipt of atemperature sensor signal from a port indicating an applicator isconnected to that port, and wherein the controller is programmed todetermine from a determination of the number of applicators connected tothe multiplexer and power splitting circuit and the particular outputports to which the applicators are connected, whether when only a singleapplicator is detected, the single applicator is properly connected tothe single connection applicator output port and whether when aplurality of applicators are detected, the plurality of applicators areproperly connected to only the multiple connection output ports, andprovide an output signal indicating if the applicators are not properlyconnected.
 26. A system for microwave therapy for heat treatment ofdiseased tissue within a living body according to claim 20, wherein theapplicator additionally includes an outer conductive sleeve extendingaround and spaced from the outside surface of the microwave energytransmission line to form an outside of a portion of the elongateapplicator body and to provide a cooling fluid space between the outsidesurface of the microwave transmission line and an inside surface of theouter conductive sleeve, and a guide sleeve positioned concentricallyaround and spaced from the outside surface of the microwave energytransmission line and the inside surface of the outer conductive sleeveto divide at least a portion of the cooling fluid space into an innercooling fluid space along the outside surface of the microwave energytransmission line and an outer cooling fluid space along the insidesurface of the outer conductive sleeve, said inner cooling fluid spacecommunicating with said outer cooling fluid space whereby said guidesleeve is adapted to guide flow of a cooling fluid within the coolingfluid space to cool the microwave energy transmission line and the outerconductive sleeve; and wherein the temperature sensor is positioned tomeasure the approximate temperature of a cooling fluid when a coolingfluid is present in the cooling fluid space during operation of theapplicator.
 27. A system for microwave therapy for heat treatment ofdiseased tissue within a living body according to claim 26, wherein theelongate applicator body additionally includes depth markings visible onthe outside of the elongate applicator body and spaced at regularintervals along the elongate applicator body as a guide to the depth towhich the elongate applicator body is inserted into the living body, andadditionally including a cadence sound generator which generates aregular cadence sound, whereby the regular cadence sounds, incooperation with the regularly spaced depth markings, are adapted beused during withdrawal of the applicator to withdraw the applicator at asubstantially constant predetermined rate, which, if done with microwavepower applied to the applicator will provide track ablation along theinsertion track during withdrawal of the applicator along the insertiontrack.
 28. A system for microwave therapy for heat treatment of diseasedtissue within a living body according to claim 27, wherein the cadencesound generator is provided as part of the system controller.
 29. Asystem for microwave therapy for heat treatment of diseased tissuewithin a living body according to claim 20, wherein the elongateapplicator body additionally includes depth markings visible on theoutside of the elongate applicator body and spaced at regular intervalsalong the elongate applicator body as a guide to the depth to which theelongate applicator body is inserted into the living body, andadditionally including a cadence sound generator which generates aregular cadence sound, whereby the regular cadence sounds in cooperationwith the regularly spaced depth markings are adapted to be used duringwithdrawal of the applicator to withdraw the applicator at asubstantially constant predetermined rate, which, if done with microwavepower applied to the applicator, will provide track ablation along theinsertion track during withdrawal of the applicator along the insertiontrack.
 30. A system for microwave therapy for heat treatment of diseasedtissue within a living body according to claim 29, wherein the cadencesound generator is provided as part of the system controller.
 31. Asystem for microwave therapy for heat treatment of diseased tissuewithin a living body, the system comprising: a) a microwave generatorfor outputting microwave energy; b) at least one microwave applicatorcomprising: i) an elongate applicator body having an insertion end forinsertion into a tissue region of the living body and an attachment endfor attachment to the coaxial microwave energy supply cable; ii) anantenna for radiating microwave energy disposed toward the insertion endof the applicator body; iii) a microwave energy transmission linedisposed within the elongate applicator body to conduct microwave energyfrom the attachment end of the applicator to the antenna, said microwaveenergy transmission line having an outside surface and an innerconductor and an outer conductor; c) a system controller coupled to themicrowave generator for controlling system operation; and d) at leastone power splitter circuit for coupling the microwave energy generatorto at least one coaxial microwave energy supply cable for supplyingmicrowave energy from the microwave generator to the microwaveapplicator, said at least one power splitter circuit having a microwavepower input connected to the microwave generator and a plurality ofoutput ports, wherein one of the plurality of output ports is a singleconnection output port for use where only a single coaxial microwaveenergy supply cable and microwave applicator is connected to the powersplitter circuit, and the remaining output ports of the plurality ofoutput ports are multiple connection output ports for use where two ormore coaxial microwave energy supply cables and microwave applicatorsare connected to two or more multiple connection output ports of thepower splitter circuit, and wherein the single connection output port isimpedance matched and tuned to provide efficient energy transfer whenusing a single applicator and the multiple connection outlet ports areimpedance matched and tuned to provide efficient energy transfer whenusing a number of applicators anywhere from two to the total number ofmultiple connection output ports provided.
 32. A system for microwavetherapy for heat treatment of diseased tissue within a living bodyaccording to claim 31, wherein the power splitter circuit includes onesingle connection output port and three multiple connection output portsto allow attachment of a single applicator to the one single connectionoutput port, two applicators to two of the multiple connection outputports, or three applicators to three of the multiple connection outputports of the power splitter circuit to provide one, two, or threeapplicators connected to the power splitter circuit.
 33. A system formicrowave therapy for heat treatment of diseased tissue within a livingbody according to claim 32, wherein the impedance through the powersplitter circuit for the single connection output port is about fiftyohms with an electrical length delay of about one hundred eightydegrees, and the impedance through the power splitter circuit for eachof the three multiple connection output ports is configured in twosections, a microwave input section having an impedance of between aboutseventy and ninety ohms with an electrical length delay of about ninetydegrees, and a microwave output section having an impedance of aboutfifty ohms with an electrical length delay of about ninety degrees. 34.A method for providing microwave therapy for heat treatment of diseasedtissue in a living body and of providing cooling along a portion of anelongate microwave applicator adapted for insertion into living bodytissue, comprising: obtaining a microwave applicator including anelongate applicator body having an insertion end for insertion into atissue region of the living body and an attachment end for attachment toa source of microwave energy; an antenna for radiating microwave energydisposed toward the insertion end of the applicator body; a microwaveenergy transmission line disposed within the elongate applicator body toconduct microwave energy from the attachment end of the applicator tothe antenna, said microwave energy transmission line having an outsidesurface; an outer conductive sleeve extending around and spaced from theoutside surface of the microwave energy transmission line to form anoutside of a portion of the elongate applicator body and to provide acooling fluid space between the outside surface of the microwavetransmission line and an inside surface of the outer conductive sleeve,said cooling fluid space not extending around the antenna; and a guidesleeve positioned concentrically around and spaced from the outsidesurface of the microwave energy transmission line and the inside surfaceof the outer conductive sleeve to divide at least a portion of thecooling fluid space into an inner cooling fluid space along the outsidesurface of the microwave energy transmission line and an outer coolingfluid space along the inside surface of the outer conductive sleeve,said inner cooling fluid space communicating with said outer coolingfluid space; inserting the antenna portion of the microwave applicatorinto living body tissue to be treated and supplying microwave energy tothe antenna to heat the tissue to be treated; and circulating a coolingfluid through the inner cooling fluid space and outer cooling fluidspace, in either direction, during the application of microwave energyto cool the potion of the microwave energy transmission line and theouter conductive sleeve along the cooling fluid space.
 35. A method forproviding microwave therapy for heat treatment of diseased tissue in aliving body and of providing cooling along a portion of an elongatemicrowave applicator adapted for insertion into living body tissue,according to claim 34, additionally including the step of measuring theapproximate temperature of the cooling fluid during operation of theapplicator and using the temperature measured as an indication ofwhether cooling fluid is actually circulating in the cooling fluidspace.
 36. A method for providing a microwave therapy system forefficient heat treatment of diseased tissue in a living body when usingone or more microwave applicators, comprising: providing a microwavegenerator for generating microwave energy to be transmitted to aselected number of microwave applicators; providing a power splittingcircuit having an input for connection to the microwave generator andone single connection output port and a plurality of multiple connectionoutput ports; providing a microwave conduction path between the inputand the single connection output port having an effective impedance andtuned for connection of a single microwave applicator through amicrowave energy supply cable connected to the single connection outputport; and providing microwave conduction paths between the input and theremaining two or more multiple connection output ports having aneffective impedance and tuned for connection of two or more microwaveapplicators to two or more multiple connection output ports with noconnections to the other output ports.
 37. A method for providingmicrowave therapy for heat treatment of diseased tissue in a living bodyand for providing track ablation during removal of a microwaveapplicator from treated tissue, comprising: obtaining a microwaveapplicator to be inserted into diseased tissue to be treated in a livingbody wherein the applicator includes regularly spaced depth markingsalong the applicator used as an indication of the depth of insertion ofthe applicator into the living body; obtaining a cadence sound generatorfor producing an audible sound at regular intervals; inserting theobtained microwave applicator into the tissue to be treated in theliving body whereby an insertion track is formed through the living bodyinto the tissue to be treated by the insertion; supplying microwaveenergy to the applicator to heat and treat the tissue to be treated;after completion of the treatment of the diseased tissue, supplyingmicrowave power to the applicator and operating the cadence soundgenerator to produce the cadence sound, and with the microwave powersupplied to the applicator, withdrawing the applicator from the treatedtissue at a substantially constant desired rate by using the cadencesounds in conjunction with the regular depth markings to establish theconstant rate to thereby provide ablation along the insertion track asthe applicator is being withdrawn.
 38. A method for providing microwavetherapy for heat treatment of diseased tissue in a living body and forproviding track ablation during removal of a microwave applicator fromtreated tissue, according to claim 37, wherein the step of obtaining amicrowave applicator including regularly spaced depth markings along theapplicator is the step of obtaining a microwave applicator having depthmarkings at regular one cm spacing, and the step of obtaining a cadencesound generator for producing an audible sound at regular intervals isthe step of obtaining a cadence sound generator for producing an audiblesound at regular intervals produces audible sounds at one secondintervals.